<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let arr = [88, 20, 10, 100, 50]
        function findIndex(list) {
            for (let i = 0; i < list.length; i++) {
                console.log(list)
                if (list[i] === 10) {
                    document.write(`元素为10的下标${i}<br>`)
                } else {
                    document.write(`元素为${list[i]},-1<br>`)
                }
            }
            return arr

        }
        let re = findIndex(arr)


    </script>

</body>

</html>